The present invention relates to a method of producing alkylene glycol monosorbates and a method of preserving the monosorbates.
More particularly, the present invention relates to a method of producing alkylene glycol monosorbates such as hydroxyethyl sorbate, hydroxypropyl sorbate, hydroxybutyl sorbate and the like from sorbic acid and alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide and the like and to a method of reserving the alkylene glycol monosorbates.
Since alkylene glycol monosorbates have two conjugated double bonds in their structure, the compounds are expected to be used in many fields as functional monomers. However, a few methods of producing the compounds were disclosed as shown in the following and a method of preserving the compounds was not disclosed at all.
In relation to a method of producing an alkylene glycol monosorbate, a method of reacting sorbyl chloride and an alkylene diol is reported (Zh. Prikim (legirad) 46 (5) 1099-1103 and Eur. J. Med. Chem. Ther. 18 (5) 441-445 (1983)), and a method in which butanediol monoester is synthesized from sorbic acid and butanediol in the presence of an acylating agent is disclosed (Japanese Laid-Open Patent Application No. 60-252448).
In these conventional methods, the method of producing an alkylene glycol monosorbate, in which sorbyl chloride and an alkylene diol are reacted, has a problem that hydrogen chloride is produced and additional processes are required to remove it because sorbyl chloride is used as a raw material. The method has further problems that isolation of the alkylene glycol monosorbate produced is difficult and the yield is lowered. As a result, the method is not effective industrially. On the other hand, the method of producing butanediol monoester, in which sorbic acid and butanediol are reacted, has problems in that an expensive acylating agent is required and that the yield of the separated product is lowered. As a result, the method is also not effective industrially.